The invention relates generally to an adapter for positioning a lens. More specifically, the invention relates to an adapter in a motion sensor module for positioning a lens to a predetermined position relative to a sensor attached to a circuit board, and for shielding the sensor from air currents. The adapter is funnel-shaped, holds a lens on a front side, and has a shroud on the opposite back side for shielding the sensor from air currents. The shroud also has pins that are inserted through a circuit board for maintaining the adapter in a predetermined position, and each pin can have a stop that determines the distance between the lens and the sensor.
Passive infrared sensors are commonly used in motion detectors to determine the presence or absence of individuals, generally determining if someone enters a zone of coverage. These detectors may be connected to security systems, and thereby alerting others of intrusion into the zone, or they may be connected to light switches, and may be used to turn lights on when a person is present in the zone, or deactivate the lights when a person is no longer present in the zone.
These motion detectors generally consist of a housing, and have a passive infrared sensor attached to a printed circuit board contained in the housing. A lens is positioned in front of the sensor, the lens focusing the infrared profile of a person as it moves across the field of view. The sensor is positioned near the focal point of the lens. A lens retainer allows the lens to be fixed in a predetermined position and assists in reflecting infrared towards the sensor.
However, tolerance buildup during manufacture can alter the predetermined lens position. Additionally, air currents passing over the sensor can result in false sensor readings. Consequently, there is a need for an adapter that accurately positions the lens to a predetermined focal point relative to the sensor, and a shroud for reducing or eliminating stay air currents from around the sensor.
Some examples of passive infrared motion detectors are U.S. Pat. No. 5,764,146 to Baldwin et al.; U.S. Pat. No. 4,672,206 to Suzuki et al.; U.S. Pat. No. 5,442,178 to Baldwin; U.S. Pat. No. 5,626,417 to McCavit; U.S. Pat. No. 5,772,326 to Batko et al.; U.S. Pat. No. 5,790,040 to Kreier et al; and U.S. Pat. No. 5,026,990 to Marman et al, the disclosures of which are incorporated herein by reference.
One object of the present invention is to provide an improved adapter for positioning a lens.
Another object of the present invention is to provide an improved adapter for positioning a lens having projections for positioning a lens a predetermined distance from a sensor.
The forgoing objects are basically attained by providing an adapter comprising a cover having a wall forming a hollow cavity and extending about the central axis; an extension coupled to and extending from the cover, the extension having a front side with a first opening and a back side with a second opening, the first opening being smaller than the second opening, the extension being attached to the cover at the back side with the second opening being aligned with the hollow cavity of the cover; and a plurality of projections coupled to the cover, each of the projections being spaced from each other and projecting from the cover in the direction of the central axis, opposite the extension.
The foregoing objects are also attained by providing a sensor assembly, comprising a circuit board; a sensor coupled to the circuit board; an adapter coupled to the circuit board and having a cover, an extension, and at least one projection, the cover having a wall extending around the sensor, the extension coupled to and extending from the cover and having a front side with a first opening and a back side with a second opening, the first opening being smaller than the second opening, the extension being attached to the cover at the back side with the second opening being aligned with the sensor, and the at least one projection coupled to the cover and attached directly to the circuit board.
The foregoing objects are also attained by providing a sensor assembly, having a circuit board; a sensor coupled to the circuit board, an adapter coupled to the circuit board; a lens coupled to the adapter; and means for accurately positioning the lens relative to the sensor and for prohibiting air currents from interfering with the functioning of the sensor.
Other advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.